Toxicity induced by multiple high doses of vitamin B12 during pernicious anemia treatment: a case report.

The clinical consequences of excess vitamin B₁₂ induced by multiple oral doses of cyanocobalamin are not well-known.

A young woman was treated with multiple daily doses of 1 mg of cyanocobalamin for severe pernicious anemia. After a total dose of 12 mg, she developed acne, palpitations, anxiety, akathisia, facial ruddiness, headache, and insomnia. She improved two weeks after stopping the drug. There were no sequelae nor complications.Although these symptoms of cobalamin toxicity were unexpected and unusual, the case reminds us that the administration of any drug is not entirely safe.